Log in/out, multiple people per computer

Is it possible to log out without deleting the cookie.... My friend wanted to post the other day when he was over here, but we couldn't figure out how I could log out and him in. If this isn't possible it is something you guys might want to think about :D

if u go to home,
and then on the left side there is a "options" window
and the last link reads "log out"
click it and
TaDa!
your logged out!
then just log in with the other user and he/she will be able to post...
not to complicated...